The invention concerns a moisture reduction press for the separation of liquid from substances, comprising at least a first container with an inlet opening through which the substance is fed to an inlet chamber, and with an discharge opening from an outlet chamber through which the liquid-reduced substance leaves the press, that inside the first container there is disposed at least one second container so that between the surface of the first container and the outer surface of the second container there is formed a passageway, that the moisture reduction press comprises a valve/throttle provided at the discharge opening/outlet chamber and a pump unit provided at the inlet opening which valve/throttle and pump units build up a pressure at least in the passageway.
Such a moisture reduction press is known, partly for example from U.S. Pat. No. 3,982,483. The reduction press disclosed in this publication consists of a chamber in which there is provided a rotating worm-blade which, among other things, surrounds a cone. The press functions by leading the substance into a container via a form of drive and, as a consequence of the rotation of the wormblade, a feeding forward of the substance takes place. The cone will press the substance out towards the periphery of the container, and by this movement the moisture from the substance is pressed out.
The system suffers the disadvantage that the moisture can be pressed out solely as a result of the space between the cone and wall being reduced during the forward movement of the substance. There hereby arises a risk of stoppage, and the movement will also be disrupted so that the substance will not be fed forward.
Furthermore, the size of the cone must be selected in relation to the degree of moisture in the substance. In other words, this means that if the substance has a moistness which is not suitable for the relevant cone, the machinery will not function in an optimum manner, and in the worst case there will not occur any draining-off of the material.
From EP-A-0 553 783 a screw type hydroextractor is known. The screw type has the disadvantage that when for instance sludge is discharged into the first cylindrical casing the draining takes place during a press process where the material is gradually compressed and squeezed from the screw vane, i.e. dehydrating is a function of the screw vane, and it is not possible to build up a certain pressure, and it is not possible to control the draining during the draining process.
JP A 61-259 897 discloses a screw conveyor suitable for dehydrating substances. However, the construction is so that the pressure is only partly obtained from a valve and by regulating the valve at the outlet opening and pump units at the inlet opening. The rest of the pressure is obtained from the screw itself. In this way a pressure between the screw and the valve will change progressively so that the pressure at the beginning of the dehydrating process will be much smaller than that at the end. Therefore, the construction is not suitable for lumpy and viscous material since there will be a risk of hindering the movement of the screw. Secondly, since there are only small areas with through-going passages for dehydrating the substances the pump will not be very effective.
It is the object of the present invention to provide a moisture reduction press which is not encumbered with the disadvantages of the known systems. This object is achieved with a moisture reduction press of the kind disclosed in the introduction and where the wall of at least the one container, essentially for the whole of its circumference and at least between the two chambers, is produced with through-going passages and that the substances via the inlet opening is pressed into the passageway between the first and the second container and that the wall of the first and/or the second container, and which is relatively movable in relation to a scraper arrangement, is provided with the through-going passages. An optimization of the draining-off area is achieved, while at the same time sticky material is removed from the wall so that a stoppage is avoided.
There is hereby achieved a uniform distribution and pressing of the substance, and where the draining-off of this is not dependent on the moisture content, in that the system will function optimally regardless of the moisture percentage. Moreover, at the same time it is achieved that a draining-off and a continuous feeding forward of the substance takes place without any risk of this feeding forward being stopped.
The manner in which the moisture reduction press works is that the substance is pumped via the inlet opening into the container itself, and will be led out to the passages lying between the surfaces of the inner and the outer container, and which form an annular passageway. A regulator for the pressure in the press is provided in the other end of the press. There is now built up a suitable pressure at the same time that the material continues to be pumped in. When the desired pressure has been reached, the valve/throttle at the other end is opened so that a continuous discharge of the material takes place, during which discharge a simultaneous draining-off of the material occurs as a consequence of a pressure having been built up in the container. The important parameters for the system are namely the press pressure, the flow and time being controlled and regulated individually, and where flow and pressure are mutually dependent on one another the possibility is achieved of being able to control those of the process parameters which are of significance for the finished result, i.e. an optimum regulation of the press pressure which is built up, the regulation of the time for which the material is present in the container, plus a regulation of the flow which takes place. The process can, however, also be a pulsating continuous process, which is achieved by the valve/throttle being opened/closed intermittently.
By providing a moisture reduction press, it is achieved that the material is not pressed the easiest way through the press, which would give rise to the risk that only a part of the straining area is utilized. Moreover, a cleaning of the sieve is effected, so that this is held clean. Furthermore, the scrapers can serve to transport the material, especially if these are formed as worm blading, and finally the scrapers make it possible to empty the press when this has finished, and thus make the cleaning process easier.
By providing a moisture reduction press according to the invention, an expedient configuration of the movable parts of the press is achieved.
By providing a moisture reduction press, the possibility is achieved of leading the substance in the direction towards the discharge opening whenever this may be necessary.
By providing a moisture reduction press according to the invention, an optimization of the scraping-off effect of the scrapers is achieved, which can be particularly expedient in connection with substances which have a certain adhesive character, and for example also in connection with extremely greasy material.
By providing a moisture reduction press according to the invention, the possibility is achieved of accelerating the draining process when and underpressure is applied to the jacket.
The invention also concerns a method for the draining-off of the substance. material.
The invention will now be described in more detail with reference to the drawing, where